When connecting two or more filters, each having different band pass region, to a conventional multilayer filter, a phase shifter has been provided as an external device at the respective input/output ports in order not to affect each other's band pass region.
Further, as shown in FIG. 20, two band pass filters 61, 62 have been employed for matching the impedance so as the two band pass regions, viz. a low band pass region 31 and a high band pass region 32 of FIG. 19, do not give influence to each other.
However, if each of the input/output terminals of the respective filters is connected with an external phase shifter, the overall size of an entire filter becomes large, rendering it unsuitable for use in a mobile communication apparatus where the small-size, light-weight and thin-shape are the essential requirements.
In a configuration where two band pass filters 61, 62 are provided as shown in FIG. 20, the designing consideration is focussed only on the impedance matching between the low band pass region 31 and the high band pass region 32. Therefore, the amount of attenuation remains insufficient with respect to a band region 33 locating between the low band pass region 31 and the high band pass region 32. Thus it deteriorated the characteristics of high frequency circuit in a mobile communication apparatus.
The present invention addresses the above described drawbacks, and offers a small multilayer filter with which the amount of attenuation is sufficient in a region other than band pass region, while the insertion loss characteristic caused as a result of insertion of two or more band pass regions is not deteriorated.